Preheat your oven to 350°F (175°C) and prepare an 8×8-inch baking pan with parchment paper or light greasing.

Melt the unsalted butter and mix it with brown sugar until smooth. Add the egg and vanilla, then fold in the mashed bananas.

In another bowl, mix the flour, baking powder, baking soda, cinnamon, and salt. Gradually add this to the wet mixture.

Fold in your chosen mix-ins like chocolate chips or nuts.

Pour the batter into the prepared pan and bake for 25–30 minutes until edges are golden and a toothpick comes out mostly clean.

Let the blondies cool on a wire rack for 15–20 minutes before slicing into squares.